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Re: Arguments to foreign tables?

From: Ronan Dunklau <rdunklau(at)gmail(dot)com>
To: Jeff Davis <pgsql(at)j-davis(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Arguments to foreign tables?
Date: 2012-11-06 08:19:03
Message-ID: CAJWq4=Z0ucoAJ3wxur8fTxX4DrVYHxPuLpT7gxW60ty-R+jk3w@mail.gmail.com (view raw or flat)
Thread:
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Maybe you could set some options on the foreign table before selecting from
it ?
Another way you could achieve the same result would be to give some column
a special meaning (like it is done in the twitter_fdw for example).

If you don't mind, do you have a specific use-case for this ?

--
Ronan Dunklau

2012/11/6 Jeff Davis <pgsql(at)j-davis(dot)com>

> On Sun, 2012-11-04 at 15:13 -0500, Tom Lane wrote:
> > Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> > > Is there any fundamental or philosophical reason why a foreign table
> > > can't accept arguments?
> >
> > That isn't a table; it's some sort of function.  Now that we have
> > LATERAL, there is no good reason to contort SQL's syntax and semantics
> > in the direction you suggest.
>
> Maybe I should rephrase this as a problem with SRFs: you don't get to
> define the init/exec/end executor functions, and you don't get access to
> the optimizer information.
>
> It seems like foreign tables are a better mechanism (except for the
> simple cases where you don't care about the details), and the only thing
> an SRF can do that a foreign table can't is accept arguments. So, I
> thought maybe it would make more sense to combine the mechanisms
> somehow.
>
> Take something as simple as generate_series: right now, it materializes
> the entire thing if it's in the FROM clause, but it wouldn't need to if
> it could use the foreign table mechanism.
>
> Regards,
>         Jeff Davis
>
>
>
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